This is the custom module (Bootstrap 3 Core) for running on a Jahia server.
Is there any module that uses this bootstrap 3 core module?
Of course. You can check this one http://store.jahia.com/contents/modules-repository/org/jahia/modules/bootstrap3-components.html that offers a lot of great components.
Is there a way to customise my own CSS using fewer variables?
Yes. you can generate your own CSS file from the http://getbootstrap.com/customize/ and then put the generated CSS file directly in your template set.
= JAHIA'S DUAL LICENSING - IMPORTANT INFORMATION =
Copyright (C) 2002-2017 Jahia Solutions Group SA. All rights reserved.
THIS PROGRAM IS AVAILABLE UNDER TWO DIFFERENT LICENSES:
1/GPL OR 2/JSEL
IF YOU DECIDE TO CHOOSE THE GPL LICENSE, YOU MUST COMPLY WITH THE FOLLOWING TERMS:
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
2/ JSEL - Commercial and Supported Versions of the program
IF YOU DECIDE TO CHOOSE THE JSEL LICENSE, YOU MUST COMPLY WITH THE FOLLOWING TERMS:
Alternatively, commercial and supported versions of the program - also known as
Enterprise Distributions - must be used in accordance with the terms and conditions
contained in a separate written agreement between you and Jahia Solutions Group SA.
If you are unsure which license is appropriate for your use,
please contact the sales department at email@example.com.