what is the "group liability" charge for?

[Darren Scorpio]

It means you are in a group that owns land and that land is set to be shown on search which costs 30L so you and another person are sharing the cost. Normally it means you are one of the owners of the group but not necessarily.

[Darren Scorpio]

It means you are in a group that owns land and that land is set to be shown on search which costs 30L so you and another person are sharing the cost. Normally it means you are one of the owners of the group but not necessarily.

[Ariel Vuissent]

It means that one of the groups you have joined has group liability set to take from all members. Any fees that the group has - for instance, wanting group land shown in search - are divided throughout the group, so all members pay a small portion of those fees.
If you don't want to have to do that, you can either IM the owner of the group and ask that they disable that setting, at least for you, or - more simply - just leave the group.