Last version dates from 2012-11-19, not the fastest of releases - but seems ok. Trend Micro is involved (and offers commercial support).

It doesn't feel heavyweight to me. It does start a bunch of daemons for all of its processing and it has the client->server bit built right in. That may make it feel heavyweight, I guess. But, you don't have to use the client->server stuff if you don't want to. It'll still do all of its magic for you.

Ossec will do a lot out of the box. So, I suggest installing it with the default ruleset and the active-response stuff turned off (the installer will ask you). Then dive into the rules and ossec.conf (knowledge of regex is required).

Documentation @ http://www.ossec.net/doc/index.html