README states: "Zstandard is dual-licensed under BSD and GPLv2". Unfortunately such sentence is very unclear.

It doesn't tell whether these licenses are connected with "and" or "or".

In case you never heard that such distinction may be important here is link with explanation: https://spdx.github.io/spdx-spec/v2.3/SPDX-license-expressions/ , see section "D.4 Composite license expressions".

Please note, that this distinction is extraordinary important. Such decision should not be taken lightly. "Or" means that user of zstd may choose license. "And" means that user must abide to both. Choosing "or" means that zstd is "effectively BSD", i. e. that it is distributed by permissive license. But choosing "and" makes zstd "effectively GPL", i. e. copyleft.

You may say: "but README literally says "and" ". Well, yes, naive direct reading of README may suggest that "and" is intended. But I don't think this is what you really meant. Again: choosing "and" will turn zstd into copyleft software and thus its use in proprietary products will be disallowed.

So, please choose one of these two options, fix README and widely announce result. Users should be aware of such change in any case. Again: this is very important