256 line limit is given in the changelog.
but 256 isn't nearly enough. especially if the SIMD instructions aren't working reliably and sensibly. at this point it's not clear how well they're working. working around their absence would consume a LOT more lines.
i'm likely to exceed 256 lines with most any program i'd bother to write. i wouldn't bother with any job that some set of vanilla combinators could do. i'm already over 100 lines with nothing but a reusable function to fetch a product's recipe from a recipe combinator. and that's just one small piece of the first useful program i'd write. of course it takes a lot of comment lines to keep any program organized too. and it's not clear whether those count toward the total.
implementing the device in a scripting language like lua, it's not clear to me why there should be any limit less than about 64,000 lines anyway. but i haven't looked at the source code at all.