Browsing this thread, there are quite a few reasons to include indie games on GOG (or, better yet, on a spin off like GIG). To sum up :
- price range
- indies are probably less reluctant than big publishers regarding DRM-less releases
- target communities largely overlap
- interesting for indie devs (no real alternative to Steam or home-made solutions, except maybe Desura if it takes momentum).
I say go for it if you can, GOG ! I'd certainly buy indie games here.