SPM supports 10 languages for version 2.1 and 6 more for version 3.0, what does this mean.
First off the 10 languages are English (EN), German (DE), Czech (CS), Spanish (ES), French (FR), Hungarian (HU), Japanese (JA), Portuguese (PT), Russian (RU) and Mandarin / Simplified Chinese (ZH). Additional 6 for 3.0 are Korean (KO), Danish (DA), Dutch (NL), Finnish (FI), Italian (IT), and Slovak (SK)
SPM application has to translate all the menu options, warning, error messages, field descriptions and other labels in the UI. What this allows is for the user to be able to login in the above supported languages and all the characters in the UI (other than data which I will discuss below) in that corresponding language. Below are few screen shots of how the application will behave under different languages.
As you noticed the menu options, drop down box options, field labels and other labels are in the appropriate language. The field description are part of the backend ABAP component, so if you end up creating new fields for your requirements in your data model you can maintain the description for the fields in BW ABAP layer in all the required languages.
The default logon language can be changed under Settings -> User default -> Language. Depending on how your system UME is setup your BW portal and / or BW backend will also be displayed in the corresponding language, since the logon language is associated with your ID.
The next major component of the application is master data. The system automatically looks to see if that master data text exists in the logon language, if it does not exist the system displays the ‘Key‘component of the data. In the screen shots if you notice the ‘Category’ dimension values most of the values are displayed as numbers rather than text, this indicates the master data description were not loaded in Japanese or German language.
BW system supports Unicode, which means technically you can load data in the SPM data model in languages other than the support 10 languages. But since the user can logon to SPM application using only the above 10 + 6 languages (as the menu and field labels are provided in only those languages) business will never be able to see master data descriptions in any other languages.
Now few things to consider before loading non-English characters, in BW you need to specify what are valid characters so that way your data load does not fail indicating that the system has found an invalid character. Using transaction RSKC you can specify all the specific characters that should be allowed by the system. But you can also use special phrase ALL_CAPITAL or ALL_CAPITAL_PLUS_HEX, please refer to OSS note 1075403 for more details.
As mentioned above SPM ABAP add-on delivers descriptions for the entire out of the box dimensions & measures. Basically the SPM add-on delivers descriptions for all the SPM info-objects. For this to happen it is recommended to have the necessary language packs installed prior to SPM add-on installation.