ClamAV is an anti-virus engine, which is commonly used for email and web scanning, or gateway and fileserver securing. It provides a command-line scanner, a sendmail milter, automatic signature database updates, built-in support for many archiving and container or mail encoding formats, scanning standard ELF and compressed executables, as well as common office document formats.
Python based milter for Sendmail and Postfix MTA servers to check incoming e-mails for Microsoft Office attachments. If a Microsoft Office document is attached to the e-mail, it will be scanned for suspicious VBA macro code. Files with malicious macros are, depending on configuration, either removed and replaced by harmless text files or alternatively the whole e-mail will be rejected.
OpenDKIM is an open source implementation of the DKIM (RFC6376) email sender authentication system, derived from dkim-milter. It also supports ADSP/RFC5617, Vouch by reference/RFC5518, and experimentally ATPS/RFC6541. It works with any MTA supporting the sendmail milter API, such as Postfix. OpenDKIM provides a Lua-scriptable policy engine, LDAP and SQL database support, and statistic/reporting tools.
wpkg.exe is a package manager for Windows, which is fully compatible with the Debian package format, and also implements APT-style dependency resolution. It also runs on Linux and MacOSX, and there's a graphical frontend alternatively. It supports package installation with implicit repositories over various protocols.
SmbFTPD is derived from the FTP daemon from FreeBSD 5.4. It keeps all original functionality, but adds more user permission control features, integrates config files, and a Samba-style share management approach with reusing SMB authorization. It supports TLS as ported from BSDftpd-ssl. But it's still pretty small (90KB), runs on x86, ARM and MIPS.