As far as I can see, Typo 2.5.6 (the most recently released stable version) should work fine with Rails 1.0. I just did a brief round of testing with 1.0rc2, and all of the tests pass. Er, except for one test that had a stupid typo that somehow still worked with Rails 0.13.1; the bug is in the test itself, though, so it’s not worth releasing Typo 2.5.7 just for that. If we ever release Typo 2.5.7, then I’ll make sure that the fixed test is included.
Also, Typo 2.5.6 should work just fine with Ruby 1.8.3, too, as long as you’re using Rails 1.0. I haven’t actually tested this yet, but I’d be surprised if it doesn’t work perfectly.
Surprisingly enough, the current Typo trunk (r683 or so) doesn’t work with Rails 1.0. All of the filtering code is broken; I’ll fix it shortly and check in the fix. Fortunately, the current Typo trunk is pinned to Rails 0.13.1 for now, so it should be safe to upgrade the version of Rails on the box; Typo will just ignore the new Rails for now.
Update: the Typo trunk r685 or later should be compatible with Rails 1.0rc2. I’ll probably break Rails 0.13.1 compatibility soon, so it’s time to upgrade.