Grab it here:

http://freesynd.sourceforge.net/

Dunno how complete it is at the moment.

Two things about this source port: the save format seems to be completely different. It's a .fsg extension instead of .gam, and the saves are about a tenth in size. And the documentation indicates some extra key shortcuts, but I'm not sure how many are new; the only ones listed that I know of in the original game are using 1-4 to select individual agents.

what's the point of the open source port?

it looks like the original, it needs the original files, and i see no real benefits.

The same reason can be given for all ports:
-It runs natively and does not need DOS emulation (through DOSBox). This means it uses muss less system resources. This may not be important on most Desktop computers, but many portable devices usually struggle to run 486+ DOS games fluidly in DOSBox.
-It is possible to increase the visible area for higher resolutions or widescreen
-It is possible to fix bugs or make enhancements/additions/modifications to the original game (be it content, music, graphics, game rules, levels, etc.)
-It provides a true challenge for the coders to reverse engineer and re-implement all the original program's features

Of course all that only comes to fruition once the port is finished which takes a lot of work and time. I agree that the excellent emulation through DOSBox has eliminated a lot of incentive for such ports, but the reasons above are apparently still important enough for some people to invest that kind of work and time. :)

fair enough.

what points are true for this particular port? can you play Syndicate in resolutions beyond 640x480? if yes, wouldn't that make everything tiny seeing as it is a pure 2D sprite-based game?

I gave this a go and it works really well.. however sadly the map doesn't seem to show your objective or anything other than the layout of the level.. and also no civilians move around.

Works fine otherwise though

If you're interested, there's a remake of Syndicate Wars attempted here: http://swars.vexillium.org/

Interesting. I've been modding Jagged Alliance 2 lately. Would be neat to get into modding my other favourite isometric strategy game from the 90s!

To set up and use FreeSynd with the GOG release of Syndicate Plus:

1. Download FreeSynd from the following link and extract it:
https://sourceforge.net/projects/freesynd/files/
(Note: The green button downloads an old version, so use the folder view below it to get the actual latest version)

2. Copy all files in the SYNDICAT\DATA folder of your Syndicate Plus installation to FreeSynd's bin\data folder. There should be 439 of them.

3. Download and apply the following patch by copying SOUND-0.DAT to the same folder as above, overwriting the one there:
https://community.pcgamingwiki.com/files/file/1201-syndicate-plus-patch-for-freesynd/
(That makes FreeSynd work with Syndicate Plus. If you happen to be reading this and have plain, non-Plus/GOG Syndicate, you may not need to do this step).

4. Optional: Open bin\freesynd.ini and set "fullscreen" to "true" or else the game will be in a tiny window.

5. Run bin\freesynd.exe.

FYI, it's also possible to point FreeSynd to your existing Syndicate Plus installation by editing the "data_dir" path in freesynd.ini, so that you don't have to copy the files in Step 2, but you'll then have to overwrite the file in your Syndicate Plus installation with the file in Step 3.

To note, as of 0.7.5, this open source engine is missing a lot of core functionality. Missing sound effects, panic mode, and even agent AI. Hoping a new version would be out to address these, because everything else seems great. It is significantly more responsive than the DOSBox version.

mouse grabbing tactics of the port are currently very aggressive.
if you tab out, you cant do anything with your mouse in windows.
also when you tab back you will see windows task bar with the game.