Originally posted by Andre
Or is it the case that the SCP only cares about making the game more stable, change all the typos in the Great Library and prepare it for new and better mods?
That is indeed our primary goal. Implementing new gameplay in the same way mods do is better done by mods - there are very few such changes we can agree on, so they don't fit well into a community project setting. Mods are better written by individuals (see what has been done by stankarp in AOM).
So could somebody tell me differences between the original build and the SCP build?
Not many of the fundamental changes you seem interested in, but the readme of the playtest does contain a summary of the changes which the user might be interested in. Focus on those labeled "Changed:" or "Added:", rather than "Fixed:", to see the more dramatic differences.
How does the game work if I install the Apolyton Mod over the SCP build?
Does this work?
Is there a risk of gettings unpredictable results in some cases or is this just the way I should do it?
It should work - we have tried to maintain backwards compatibility (with mixed results). The worst problem in this regard is that some SLIC constructs no longer work as they used to, which may break some features.
Please feel free to try it, and, if you encounter problems, we will do our best to fix them, bearing in mind that it is not really our job to maintain the Apolyton Pack.