I have read MuTect1 paper and MuTect2 code, and it seems the germline risk is assigned this way
1. if variants in dbsnp, but not cosmic, the nlod cutoff is 5.5
2. otherwise, the cutoff is 2.2
Some of the variants that looks like somatic, but are labelled as germline_risks, one example is
chr11 123456789 . C A . germline_risk ECNT=1;HCNT=4;MAX_ED=.;MIN_ED=.;NLOD=3.61;TLOD=12.81 GT:AD:AF:ALT_F1R2:ALT_F2R1:FOXOG:QSS:REF_F1R2:REF_F2R1 0/0:13,0:0.00:0:0:.:440,0:10:3 0/1:10,6:0.357:2:4:0.667:336,173:4:6
And I used the MuTect2 default settings initial_tumor_lod=4.0 initial_normal_lod=0.5 tumor_lod=
6.3 normal_lod=2.2 dbsnp_normal_lod=5.5