Sphider 3.1.0-MB is multibyte capable, like 3.0.0-MB. However, 3.1.0-MB does NOT require the PHP mbstring extension. Mbstring is recommended, but not required. If it is available, it will be used. If not, Sphider will emulate the mulitbyte character string functions. Also, 3.1.0-MB continues the improvements always being made to the original fork. Since there is no longer any special requirements other than the typical MySQLi/MySQLnd extensions, there is no longer a need for the 2.4.x line.
Sphider 2.4.2-PDO provides a fix for a problem with 2.4.1-PDO which could cause some UTF-8 characters to be mistaken for ISO-8859-1 characters. The resulting “conversion” produced rubbish. The PDO fork will continue to be available and supported, but no further product enhancements are anticipated.