What is a good BASIC compiler for Mac OSX?
Most of these have trial versions that you can check out for at least 30 days before deciding to buy. REALbasic is an awesome tool, and I've wanted to try Objective-Basic for a long time. KBasic looks promising, especially considering the price.
And then there's always the option of running BSD/Unix/Linux-based tools in OS X, as well as Windows programs if you have an Intel-based Mac.