I'm not too sure what this thread is about but here is some info:
There are at least a couple of good modern PC versions of Defender. Refender is very close feel to original with modern graphics and sound, and some baiter variations. Pentasma is a fun version with double fire speed. I haven't played either for more than testing purposes.
I've modified the original game in various ways, game structure, enemy mix etc. And I release them as a romspack suitable for mame or jrok. Note: Dave Langley has designed a ROM board that gives cabinet owners access to 16 (or 32) ROM versions.
Redplus has a selection of features available from the settings menu, eg skip waves, slow ramp, initial bombs, incremental humans, progressive bonus. And comes in original look, and updated bomb/ship display.
Pink ROM changes the points structure to favour defending humans, and does wave refresh every wave (giving you 1 additional human each time).
Abduction features lots of humans and lots of landers, no bombs and no bonuses. It was produced for competition days, so no one lasts more than 5 minutes.
Marathon scores up to 100M (but still has goldilocks zone every 1M). And has a ship and bomb counter. No one has clocked it.
Mayhem hasn't been released yet (there was an error first time out), but the idea was similar to that April Fool Defender 3 video. I would probably take advantage of the JROK 1.5MHz cpu mode to enable a more chaotic onslaught.
If you know someone in the facebook group WDPU, they will be able to find you these ROMs.