If you wish to incorporate 8sms into a custom Android ROM, here are some things which may be of interest.
Relevant variables in mms_config.xml
Configure whether Stand-alone mode is enabled or disabled by default
<!-- Stand-alone mode is off by default. -->
To make Stand-alone mode enabled by default, set this variable to true.
This variable only applies to Android version 4.3 and lower. It has no meaning in Android 4.4 and above.
Configure whether to show the stock app warning reminder
<!-- Display stock app warning on ConversationList screen. -->
To disable the stock app warning, set this variable to false.
Configure whether to read settings from other packages
<!-- Comma delimited list of other packages to search for mms_config.xml and load, if exists. -->
To disable reading of settings from other packages, set this variable to an empty string.
Alternate settings in mms_config_extra.xml
To make changes to just one or two settings, you can place them in mms_config_extra.xml.
You can also use resource qualifiers.
For example, placing the following:
<?xml version="1.0" encoding="utf-8"?>
into res/xml-mcc440-mnc20/mms_config_extra.xml would set the default userAgent value for mobile network with MCC 440 and MNC 20 (Softbank).