  The current limit on the tensor-to-scalar ratio from the BICEP/Keck
Collaboration (with r<0.036 at 95% confidence) puts pressure on early universe
models, with less than 10% of the error on r attributed to uncertainty in
Galactic foregrounds. We use the BICEP/Keck BK18 public multi-frequency
likelihood to test some further assumptions made in the foreground modeling,
finding little impact on the estimate for r. We then estimate
foreground-marginalized cosmic microwave background (CMB) B-mode polarization
bandpowers. We fit them with a multivariate offset-lognormal distribution and
construct a marginalized 'BK-lite' likelihood for the CMB B-mode spectrum with
no nuisance parameters, serving as a method demonstration for future analyses
of small sky regions, for example from the South Pole Observatory or CMB-S4.
