Due to plugin API incompatibility problem, we have been actively conducting research to ensure plugin compatibility. Many people suggested editing the plugins and bump the declared `main: 1.0.0` in the plugin.yml. This is very wrong. Some people also suggested editing the server software and bump the declared API_VERSION "2.1.0" to "1.0.0". This is also very wrong. The correct way should be to bump your MCPE version to alpha 0.10.4/0.10.5, the last MCPE version that PocketMine worked with. You can do this by searching your app backups for MCPE alpha 0.10.4/0.10.5. If you didn't do backups, you can consider using the method-that-cannot-be-named to get MCPE alpha 0.10.4/0.10.5. Then you can download the respective PocketMine version for that MCPE version. You can then use most plugins that declared the old API verison. Simple. This is so far the best way we have found to fix incompatibility problems. We will continue to work on finding better ways to solve the problem of plugin API incompatibility. Current research progress shows that boycotting any MCPE updates with protocol updates or feature additions would be the best fix to the problem. References: Message on #mcpedevs, @gurun, October 2015, https://botbot.me/freenode/mcpedevs/msg/52180503/
Anyways: Error 404, Stable PM for 0.10.5 not found. Please use 0.10.4. The phar for 0.10.4 can be downloaded here: Phar download [Details: This version is using API 1.11.0, and was released on Tue, 17 Mar 2015 17:00:47 GMT] If you want to use a BETA build, here you go: Phar download Please note that this version is never going to be supported, was never supported and crashes if you spawn below 0. [Details: The build 936 using API 1.11.0 was released on Tue, 06 Jan 2015 18:44:08 GMT] Truly fucking hilarious.
A working method... But to tell the truth, not very practical. You can hardly expect everyone who wants to play on a certain server or someone who wants to make a popular server to downgrade that much. But then again, there are also plenty of new plugins and plenty of people who could make new plugins.