This is the official trademark policy for ZeroMQ:
1. The name "ZeroMQ" was a trademark owned by iMatix Corporation until May 12, 2022. The mark is now available for free use in connection with ZeroMQ software and refers to either (a) the original libzmq C++ library, or (b) the community of projects hosted in the https://github.com/zeromq organization.
1.2. The name "0MQ" and the "ØMQ" logo (logo from three stylised letters) was a trademark owned by iMatix Corporation until Sep. 18, 2020. The mark is now available for free use in connection with ZeroMQ software, the "ØMQ" logo (black or red colour RGB(255,0,0)) in particular is to be used in compliance with creative commons license Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) (reuse the work for any purpose, including commercially; however, it cannot be shared with others in adapted form, and credit must be provided).
1.3. The freestanding single letter "slashed O" or "Ø" never was a feature of the mark—not even as logo, not even the color red. It is for free use in connection with ZeroMQ software.
2. "ZMTP" refers to the ZeroMQ Message Transfer Protocol, or ZMTP, as defined by http://rfc.zeromq.org/spec:37 and related documents.
3. "The Protocol of Things" refers to the ZeroMQ Message Transfer Protocol, or ZMTP, as defined by http://rfc.zeromq.org/spec:37 and related documents.
4. The intent of this trademark policy is to avoid confusion from inappropriate use of these marks, and to ensure that the ZeroMQ mark is an accurate indicator of the origin of the software.
5. You are granted the right to use the "ZeroMQ" marks in all their forms to discuss, describe, document, or refer to projects hosted in the ZeroMQ community, or projects that build on those projects.
6. You may write "ZeroMQ" and "ØMQ"; other upper/lower case combinations such as "0mq" or "Zeromq" are not correct, and not allowed. The preferred written form is "ZeroMQ."
7. You may use "ZMTP", "zmtp", and "the Protocol of Things" in the name or description of any product (public or private) that conforms to the ZMTP specifications (including partial implementations).
8. You may not use the name "ZeroMQ" in any other software project name, not in any web site outside the zeromq.org domain, except as granted in (5).
9. If you make products that build on top of libzmq, you may not call them "ZeroMQ". The conventional naming scheme for language bindings, for example, is "abczmq" where "abc" is the abbreviation for the language.