My very rough understanding, is those particular gentleman got arrested for printing the magazine Grenzfal which was raising awareness on topics such as pollution, deforestation, and the impact of industrial activities on the environment.

The Environmental Library, located within the Zion Church, was a particular point of interest for the Stasi. The library's focus on environmental issues and its role in raising awareness about ecological problems were seen as subversive by the authorities.

And yes, I believe they got released.