While UP's work is great, it takes some liberties on what should and shouldn't be. Even if "-game Vampire" is used, some of the original files are overwritten by any UP install.

My question is: Is it a mandatory install or does GOG also provide an original (untouched) version of the game? Even if it means it doesn't run at all on modern computers?

Edit: Grammar.

The Unofficial Patch and thus also the GOG releases include all the original files as a backup, they have the endings ".12" as they stem from the last official patch 1.2. Just remove ".12" and replace the modified patch files with those and try getting it to work!

My concern is about various files under the Vampire folder. Unofficial Patch's base install includes various files (client.dll, vampire.dll, two vpks, nodegraphs...) which would just overwrite the base ones at installation.

Call me nitpicky but I'm just confused by GOG's preservation program.

As I wrote, the dll files have their 1.2 patch backups included and the patch never touched the others.

When installing the latest basic Unofficial Patch I get those files:

.\Vampire\pack102.vpk
.\Vampire\pack103.vpk
.\Vampire\cl_dlls\client.dll
.\Vampire\cl_dlls\client.dll.12
.\Vampire\cl_dlls\GameUI.dll
.\Vampire\cl_dlls\GameUI.dll.12
.\Vampire\dlls\vampire.dll
.\Vampire\dlls\vampire.dll.12
.\Vampire\maps\graphs\ch_cloud_1.ain
.\Vampire\maps\graphs\ch_dragon_1.ain
.\Vampire\maps\graphs\ch_fishmarket_1.ain
.\Vampire\maps\graphs\ch_fulab_1.ain
.\Vampire\maps\graphs\ch_glaze_1.ain
.\Vampire\maps\graphs\ch_hub_1.ain
.\Vampire\maps\graphs\ch_lotus_1.ain
.\Vampire\maps\graphs\ch_ramen_1.ain
.\Vampire\maps\graphs\ch_shrekhub.ain
.\Vampire\maps\graphs\ch_temple_1.ain
.\Vampire\maps\graphs\ch_temple_2.ain
.\Vampire\maps\graphs\ch_temple_3.ain
.\Vampire\maps\graphs\ch_temple_4.ain
.\Vampire\maps\graphs\ch_tsengs_1.ain
.\Vampire\maps\graphs\ch_zhaos_1.ain
.\Vampire\maps\graphs\hw_609_1.ain
.\Vampire\maps\graphs\hw_ash_sewer_1.ain
.\Vampire\maps\graphs\hw_asphole_1.ain
.\Vampire\maps\graphs\hw_cemetery_1.ain
.\Vampire\maps\graphs\hw_chinese_1.ain
.\Vampire\maps\graphs\hw_hub_1.ain
.\Vampire\maps\graphs\hw_jewelry_1.ain
.\Vampire\maps\graphs\hw_luckystar_1.ain
.\Vampire\maps\graphs\hw_metalhead_1.ain
.\Vampire\maps\graphs\hw_netcafe_1.ain
.\Vampire\maps\graphs\hw_redspot_1.ain
.\Vampire\maps\graphs\hw_sinbin_1.ain
.\Vampire\maps\graphs\hw_tawni_1.ain
.\Vampire\maps\graphs\hw_vesuvius_1.ain
.\Vampire\maps\graphs\hw_warrens_1.ain
.\Vampire\maps\graphs\hw_warrens_2.ain
.\Vampire\maps\graphs\hw_warrens_3.ain
.\Vampire\maps\graphs\hw_warrens_4.ain
.\Vampire\maps\graphs\hw_warrens_5.ain
.\Vampire\maps\graphs\la_abandoned_building_1.ain
.\Vampire\maps\graphs\la_bradbury_2.ain
.\Vampire\maps\graphs\la_bradbury_3.ain
.\Vampire\maps\graphs\la_chantry_1.ain
.\Vampire\maps\graphs\la_confession_1.ain
.\Vampire\maps\graphs\la_crackhouse_1.ain
.\Vampire\maps\graphs\la_dane_1.ain
.\Vampire\maps\graphs\la_empire_1.ain
.\Vampire\maps\graphs\la_empire_2.ain
.\Vampire\maps\graphs\la_empire_3.ain
.\Vampire\maps\graphs\la_expipe_1.ain
.\Vampire\maps\graphs\la_hospital_1.ain
.\Vampire\maps\graphs\la_hub_1.ain
.\Vampire\maps\graphs\la_malkavian_1.ain
.\Vampire\maps\graphs\la_malkavian_2.ain
.\Vampire\maps\graphs\la_malkavian_3.ain
.\Vampire\maps\graphs\la_malkavian_4.ain
.\Vampire\maps\graphs\la_malkavian_5.ain
.\Vampire\maps\graphs\la_museum_1.ain
.\Vampire\maps\graphs\la_parkinggarage_1.ain
.\Vampire\maps\graphs\la_plaguebearer_sewer_1.ain
.\Vampire\maps\graphs\la_skyline_1.ain
.\Vampire\maps\graphs\la_ventruetower_1.ain
.\Vampire\maps\graphs\la_ventruetower_1b.ain
.\Vampire\maps\graphs\la_ventruetower_2.ain
.\Vampire\maps\graphs\la_ventruetower_3.ain
.\Vampire\maps\graphs\sm_apartment_1.ain
.\Vampire\maps\graphs\sm_asylum_1.ain
.\Vampire\maps\graphs\sm_bailbonds_1.ain
.\Vampire\maps\graphs\sm_basement_1.ain
.\Vampire\maps\graphs\sm_beachhouse_1.ain
.\Vampire\maps\graphs\sm_diner_1.ain
.\Vampire\maps\graphs\sm_gallery_1.ain
.\Vampire\maps\graphs\sm_hub_1.ain
.\Vampire\maps\graphs\sm_hub_2.ain
.\Vampire\maps\graphs\sm_junkyard_1.ain
.\Vampire\maps\graphs\sm_medical_1.ain
.\Vampire\maps\graphs\sm_oceanhouse_1.ain
.\Vampire\maps\graphs\sm_oceanhouse_2.ain
.\Vampire\maps\graphs\sm_pawnshop_1.ain
.\Vampire\maps\graphs\sm_pawnshop_2.ain
.\Vampire\maps\graphs\sm_pier_1.ain
.\Vampire\maps\graphs\sm_shreknet_1.ain
.\Vampire\maps\graphs\sm_tattoo.ain
.\Vampire\maps\graphs\sm_vamparena.ain
.\Vampire\maps\graphs\sm_warehouse_1.ain
.\Vampire\maps\graphs\sp_endsequences_a.ain
.\Vampire\maps\graphs\sp_endsequences_b.ain
.\Vampire\maps\graphs\sp_epilogue.ain
.\Vampire\maps\graphs\sp_genesisdevice_1.ain
.\Vampire\maps\graphs\sp_giovanni_1.ain
.\Vampire\maps\graphs\sp_giovanni_2a.ain
.\Vampire\maps\graphs\sp_giovanni_2b.ain
.\Vampire\maps\graphs\sp_giovanni_3.ain
.\Vampire\maps\graphs\sp_giovanni_4.ain
.\Vampire\maps\graphs\sp_giovanni_5.ain
.\Vampire\maps\graphs\sp_masquerade_1.ain
.\Vampire\maps\graphs\sp_ninesintro.ain
.\Vampire\maps\graphs\sp_observatory_1.ain
.\Vampire\maps\graphs\sp_observatory_2.ain
.\Vampire\maps\graphs\sp_soc_1.ain
.\Vampire\maps\graphs\sp_soc_2.ain
.\Vampire\maps\graphs\sp_soc_3.ain
.\Vampire\maps\graphs\sp_soc_4.ain
.\Vampire\maps\graphs\sp_taxiride.ain
.\Vampire\maps\graphs\sp_theatre.ain
.\Vampire\maps\graphs\sp_tutorial_1.ain
.\Vampire\python\vamputil.py
.\Vampire\python\warrens\warrens.py
.\Vampire\resource\gameui_english.txt
.\Vampire\resource\optionssubgameplay.res
.\Vampire\resource\optionssubvideo.res
.\Vampire\resource\trackerscheme.res
.\Vampire\scripts\liblist.gam

I haven't checked every files but client.dll, vampire.dll and gameui.dll definitely differ from Steam's latest depot by a lot. Why are those files here? What version do these files come from?

.12 and last depot files don't match either, some are 2MB bigger. None of these files require any edit either for an entire playthrough to be completed on modern hardware. Only engine.dll for the game to start and optionally, shaderapidx9.dll to get high-resolution textures to load on > 4 GB RAM systems.

This discussion leads nowhere and you've started being needlessly condescending so I'll just conclude the answer to my question is: no.

I guess I misunderstood preservation as "preserving the last known version" when it actually meant "distributing custom abandonwares spins". Good to know!

"What I tell you three times is true."

The basic part of the unofficial patch ONLY contains fixes. The PLUS part is the one that restores half done stuff and such.

The GOG download does contain the original files but renamed if there was a change to them.

The change was obviously done by Valve if you compare them to the Steam files. The backup files are from the last original Troika 1.2 patch! Also there were other fixes necessary like for stats in client.dll and lights-through-wall, LOD and save speed in engine.dll.