Feb. 19 2020:
Mac OS X Build of Release v0.17.1.0. This should be compatible with MacOS X 10.10 - 10.15 and later;
April 28, 2021 Added:
Linux x64 Build of Release v0.17.1.0. This was built and tested under Ubuntu 20.04.
MacOS notes:
...however the .dmg uses APFS, and will need 10.13 or later to mount. If you get a "No Mountable File Systems" error, your OS X version is too old. (I'll look at a secondary distribution format for those people.)
Linux notes:
This should work under Ubuntu 18.04 and other distros too.
If you have an existing chain downloaded, there is a very good chance that during the block validation you will get an error which causes the client to close. This normal as there is a good chance that you might have invalid blocks previously downloaded, as the old client did not validate the blockchain.
Just restart the mooncoin client to download a valid chain from the network.