Generally a good and well-structured paper. A few typographical errors which can be quickly corrected. A few statements which are somewhat questionable, which however can probably be addressed with a suitable reference.

The results shown do not demonstrate any new physical findings, but rather validate the solver. The addition of a general lifting line solver to OpenFAST is welcome and will help contribute to the uptake of vortex methods.

Interesting paper showing a very useful update to the OpenFAST software suite. 

General comments:

-Although this is a great addition to the public available OpenFAST software, it would be great to make the novelty of the research in the paper stand out better. The methods presented are mostly already used in wind energy and there could be more emphasis on new scientific findings obtained using this tool. It is recommended to focus more on the novelty aspect to make a better contribution to wind energy sciences.

-In the specific cases many open ends are described which should be topic of future research. Although very difficult, it would be helpful if the paper can be more conclusive on some sub-topics to progress beyond the current state of the art.

Specific comments

-The 'we'-form is widely used throughout the paper which to the reviewers opinion should be prevented.

-Section 3.2

Would it be interesting to showcase the effect of regularization parameters for a wind turbine application rather than for an elliptical wing?

-Section 3.3

Can the authors comment on the discrepancy between OLAF and BEM observed in Figure 4? Should these models give identical results for a constant and uniform wind case or not?