I can download the Reforced version of Spellforce 3. Do I have to buy the expansions, Soul Harvest and Fallen

God, again? Will these expansions be rereleased in the Reforced version. Can someone please answer this?

Cant confirm for in-game content. Technically those expansions are completely stand-alone differ games. They are not DLC for base game. Technically they - separate installers - not included in Reforced game and Reforced store package. But Reforced can include them as in-game content like "Gold Edition". This is unclear how much included.

Some Expansion's and DLC's are mentioned in game files. Can be seen here:
http://www.gogdb.org/products?search=spellforce
But even with that - there is always be a differences. SpellForce 2: Shadow Wars (which one is not available anymore) is Shadow Wars, SF2 Anniversary is SF2 Anniversary - they are never be 100% equal.

If you already own Soul Harvest and Fallen Gods, you don't have to repurchase. It should integrate with Reforced. There's a big "but", though. The GOG version of Reforced is bugged at launch, so it's not detecting ownership of SH and FG. Devs said they're looking into it. As of this reply, it hasn't been fixed yet. So the original campaign is working right now, DLC integration isn't, but it should be soon.

So what is really in the Reforced edition?
The download file has 41,37GB yet the original game had only 10,81GB.
So what is within those extra 30GB? Has it changed that much from the "Legacy" version?

It's huge because Reforced includes the assets from both expansions in it's installation. But the expansions are not usable in the GOG version of Reforced because it doesn't properly detect if you own them and provides no way of unlocking them.

So it's just wasting 25 - 30GB of space until they implement a way for the GOG version to register ownership of the expansions. I suppose aside from multiplayer, even once fixed it will always be wasted space if you don't own the expansions.

It's just such a weird and inefficient way to release a new edition of a game. Reforced should have just automatically included both expansions with it's purchase price and only given to users that owned SF3 and both expansions. Less confusion for users, much less technical hassle for them. I don't know what the hell they were thinking.

Mike Reforced is available for original version buyers for free. If there is files but they locked - maybe it check not subscription but games installation? Files itself maybe? And that mean for GOG you forced to install them all (but only if you have them).
Im not sure if it possible for GOG Galaxy builds do detect what games are available to account. Problem is there is tehnivally no DLCs for Reforced and no DLC for SF3. Each version is separate, addond already included in Reforced. Devs should unlock them completely in Reforced. Or move old and new stand-alone games files to implemented DLC.

GOG Galaxy can detect from account and unlock\lock DLCs app type, can detect game owning for DLCs. But here is games+games+bundled DLC and they all is not use DLC app type. So if devs decide to check Legacy to grant access to Reforced - they can do this without put them in one package (how they did). But for Reforced DLC that no work.

For example how DLC should be listed as DLC
http://www.gogdb.org/product/1207664643/build/51727259307363981
They really are DLCs for Reforced, but original is stand-alone completely differ separate series installments games.
http://www.gogdb.org/products?search=spellforce

Yes GOG's DLC systems are probably the issue here and aren't providing Grimlore with the solution they want to use. It could check for the installation of the expansions but that's kind of inefficient too. GOG probably doesn't want a Galaxy only solution either.

A good DRM-Free solution would be to have unlock installers for Reforced. They would be available to download when you own Soul Harvest and Fallen God. Simply running these installers could just unlock the content for each expansion in Reforced.

one year later and they still havent fixed it as it seems. I was just googling why spellforce 3 reforced wants me to buy the two other campaigns even though I have them installed. :-(

Yeah it's pretty sad they still haven't officially solved the problem. I recently followed the instructions in the following thread to combine all the expansions into one installation and it works.

https://www.gog.com/forum/spellforce_series/solved_starting_expansion_campaigns_from_the_base_game

Thank you for pointing me to that thread!