Hi. please, help me
I copied any modules in my site folder and linked siteroot/dev/build. I have this page:
Building database test using MySQL 5.5.29-0ubuntu0.12.04.1

Creating database tables
Email_BounceRecord
File
Folder
Image
Image_Cached
Group
LoginAttempt
Member
MemberPassword
Permission
PermissionRole
PermissionRoleCode
SiteConfig
SiteTree
Field SiteTree.ClassName: changed to enum('Page','ErrorPage','SiteTree','RedirectorPage','VirtualPage','UserDefinedForm') character set utf8 collate utf8_general_ci default 'Page' (from enum('SiteTree','Page','ErrorPage','RedirectorPage','VirtualPage') character set utf8 collate utf8_general_ci default 'SiteTree')
Field SiteTree_Live.ClassName: changed to enum('Page','ErrorPage','SiteTree','RedirectorPage','VirtualPage','UserDefinedForm') character set utf8 collate utf8_general_ci default 'Page' (from enum('SiteTree','Page','ErrorPage','RedirectorPage','VirtualPage') character set utf8 collate utf8_general_ci default 'SiteTree')
Field SiteTree_versions.ClassName: changed to enum('Page','ErrorPage','SiteTree','RedirectorPage','VirtualPage','UserDefinedForm') character set utf8 collate utf8_general_ci default 'Page' (from enum('SiteTree','Page','ErrorPage','RedirectorPage','VirtualPage') character set utf8 collate utf8_general_ci default 'SiteTree')
Page
ErrorPage
RedirectorPage
VirtualPage

After that in CMS i have internal server error. Where i can see log /dev/build?

That doesn't seem like the whole output of /dev/build. You should see a Creating Records section. If you're getting an internal server error check your server logs for more information - http://doc.silverstripe.org/framework/en/topics/debugging

This error for any module:
Fatal error: Access level to NewsArticle::$db must be public (as in class Page) in C:\xampp\htdocs\silverstripe\basic-news\code\NewsArticle.php on line 69

In SS3.1 all static Vars like $db now need to be declared 'private' (used to be public).

See: http://doc.silverstripe.org/framework/en/3.1/changelogs/3.1.0 (third line in the Framework section)

Basically your error means that the NewsArticle.php code doesn't fully support version 3.1. Check if a version for SS3.1 is available. If not, try changin these statics to private in your code, and see if it now works (there may be other issues as well)

Thanks, I try changin