http://www.daggerware.com/hackmstr.htm
The perennial PalmOs application for system extensions. Written by Edward Keyes, it got up to version 0.9 before the author apparently stopped maintaining it. You install extensions (or hacks, as they are called) just like any other application; then you activate and configure them through HackMaster.
HackMaster was supposed to keep the hacks from stepping on each others toes as they often did before its inception. It generally did a good job but suffered from a few bugs of its own that could cause unexplained crashes.
When development went into sleep mode, several other groups created HackMaster replacements. The best of these, in MattBehrens' opinion, is LinkeSOFT's X-Master (http://linkesoft.com/english/xmaster/), which is FreeAsInBeer, while HackMaster was ShareWare.
HackMaster is a classic case of what happens to software that is not FreeSoftware (with source code available, usable, and distributable) that the author loses interest in, for whatever reason. It could be argued that it was more widely used than any other piece of software for PalmOs, but that didn't turn out to be enough justification for the author to continue working on it. If it was FreeSoftware, anyone could have picked it up, fixed the bugs, and distributed the fixed version for the benefit of all.
Interestingly, though PalmOs users do now have X-Master, and it is currently well-maintained and works exceptionally well, there may be a day with LinkeSOFT stops becoming interested (especially if they're not making money off it, which is the case here.) Unless LinkESOFT made X-Master FreeSoftware, it could very well end up being another HackMaster.