Since version ≥ 1.9.0 the strongly recommended method of choice to install Semantic MediaWiki (SMW) is to use the Composer software. If you have shell access to your server you do not need to download the Tarball releases provided here. Please refer to the help page on installing SMW for further details and instructions.
In case you do not have shell access to your server you will need to download the file release and install SMW manually. File releases are however only provided as a legacy service which may be discontinued at any time.
Semantic MediaWiki is released more or less regularly as a compressed archive file on SourceForge. Those stable releases are recommended for production use. The current stable release of Semantic MediaWiki can be obtained from the project's download page at GitHub. It also includes required dependencies.