What kind of "gff" format does bioawk parse?
I would consider the description there a bug. The filter is actually the strand, strand is the frame, group is the attribute, and attribute does nothing. These are really meant to be the 9 columns.

Edit: There's a bug report related to this.

Edit 2: I've made a pull request to clarify this and fix the aforementioned bug report.

Edit 3: I realized that I never directly answered the title of your question (mea culpa). bioawk itself will work with gff, gff3, or gtf files. It really is just treating them as tab-separated files with named columns (this is surprisingly convenient, since it's a PITA to remember what column does what).

Edit 4: The PR has been merged. If you install from github then you'll see corrected field names.