Ok so I chuck in the towel. There is no point in developng with Seaside, Pier, Magritte, Squeak or Pharo for that matter. I don't own any of this code.
Now I am beginning to understand what I am doing wrong, I am not believing in "not invented here".
No. You want to use them because they have features that fulfil your needs along with a well known published API. I guess you don't modify linux kernel every day, but just use it (not speaking of Mac and windows).
It doesn't fulfil your needs 100%? Yes, you can try to modify some internal here and there, we all do that, it's Smalltalk anyway. If you just want to rebuild another image with same Seaside 2.8 version + your own modification, then MC1.5 might help you I guess. If you want to upgrade to Seaside 2.9, I say you will get some trouble, MC1.5 or not. That's a very common Smalltalk pattern.
Nicolas
Keith